Process of making nitric acid.



FRIEDRICH LUDWIG SCHMIDT,

OF CHA RLOTTENBUHG, GERll'iANY.

PROCESS U MAKING- lTilI'llIRllU LlitlllD.

Specification i Letters Patent.

Patented 530, Width Apimlication filed September 2%, 15308. Elsi-lat I ls. teases,

r1 all whom 'tl may concern:

Be it known that l, FRIEDRICH .liuowio SCHMIDT, a subject of the (hirman Empire, residing at (lharlottenlnirg, Germany, have nvented a certain new and useful (.lieniical Process of Making Nitric Acid, of which the following is a specification.

in the production of nitric acid by heating nitrate of sodium with sulfuric acid in retorts and distilling the resulting nitric acid, ln'sulfate of sodium is obtained as a by-product,

. which remains in the retorts in a incited con dition. lf nitrate of calcium, which can now be easily procured, is employed, sulfate of calcium is obtained Which remains in the re torts in a compact form on distilling the nitric acid. Further, as is Well known, decompositions occur in distilling the nitric acid as the result of overheating, nitrous vapors being formed, the recovery of which entails great expense and considerable labor.

I have found, that the first distillation of the nitric acid may be omitted, since the sulfate of calcium for red by the decomposition of nitrate of calcium by sulfuric acid is almost insoluble in the concentrated nitric acidobtained and that by filtering or pressing the reaction product, or subjecting it to centrifugal action, nitric acid is obtained which is almost free from calcium salts. I have furthcr found that nitrate of'calciuin can be dis solved b concentrated nitric acid, and that in this so ution of nitrate of calcium the trans formation with sulfuric acid takes place much more easily. Such a solution can be converted even in the cold with. a theoretical quantity of sulfuric acid. If the mixture is Warin'cd, the conversion takes place more quickly. Moreover the nitric acid produced in this manner from solutions of calcium nitrate in concentrated nitric acid, can be obtaincd almost free from calcium salts by simple pressing. By uslngcrystallized n1 trate of calcium or nitrate of calcium more or less tree from water, and by employing more or less concentrated sulfuric acid, to which S0,, may he added if desired, highly concentratcd nitric acid may be obtained. if pure nitrate of calcium he used for tliet'reaction, the nitric acid obtained Will be technically pure. If however the nitrate of calcium c0ntains impurities such as magnesia or other salts, some of these enter into the nitric acid.

But even this nitric acid cOntainingsmal} quantities of such impurities is immediately applicable for most industrial purposes.

free from calcium.

.in. 350 kg. nitric acid of Such nitric acid, containing magnesia, can easily be purified by distillation. ll loreovcr, if it is re "uircd to obtain chemically pure nitric ach by employing calcium nitrate containing magnesia, the new process with subsequent distillation is to be preferred to the older process, because nitric acid pre viously cleared of sulfate of calcium can be more easily distilled than acid containing such sulfate of calcium. not only is more heat necessary but losses. occur by the decomposition of the nitric acid into nitrous vapors and water as the result of local iwcrheatlng.

' Examples."

1. 23.6 kg. or, stallizecl nitrate-cl calcium. is stirred together with sulfuric acid of 66 Eli. equivalent to 9.8 log". 100% sulfuric acid for several hours. Then the solution is'brought unto about 100 3., until a filtered sanngle is asacooling the nitric acid is separated from thesullate of calcium by filtration, centrifugal action or pressure In the latter case r and the sulfate of calcium is systematically- Washed with clilutenitric acid and Water.

2. 23.6 kg. crystallized nitrate of calcium is dissolved in 20 kilos nitricacidof l/li specilic gravity, and treated with 948 kg. mono-' hydrate of sulfuric acid. the filtrate almost free from calcium, the nitric acid is separated i'roni the sulfate-of calcium by filtration, centrifu al action or pressure and the suli'atc of ca ciuin is'sys teuiatieally washed with dilute nitricacid and water.

3. lig. nitrate of ralciuin'is dissolved 55% strength. To this solution 50 lrg. of 95% sulfuric acid are added while stirring, until no more sulfate of calcium is )rccipitated even by flll'lihfii addition ol sulfuric acid. The conversion is complete in a short time. sulfate of calcium precipitates in a hydrated condition at this concentration. The nitric acid. of about 59% strength/Which is oly tained, is filtered oil and the remaining Sula fate of calcium is Washed systematically with dilute nitric acid and water. stain this exam e .tlicsulfate of calcium precipitates in a hy rated state and binds Water, the technical eliect obtained is to produce from diluted nitric acid a more concentrated acid about 55%. ll nitrate of calciurnlree fro water is employed, a still more dilute nitric acid may be used for dissolving the nitrate The separated.

of calcium, whichdilute acid can be obtained by systematicallywashing the sulfate of calcium.

What- I clainiis:

1. lhe herein described process of making nitric acid which consists by causing sulfuric acid in molecular pro ortions to react on nitrate'of calcium 1 an separatin the nitric acid thus obtained from the sulfate of cal cium by filtration and afterward Washing the sulfate of calcium: with dilute nitric acid and water.

2. The herein described process of making nitric acid which consists in dissolving nitrate of calcium in nitric acid, then by causing' the dissolved nitrate of calcium to react on sulfuric acid in molecular proportions,

lute nitric acid and water.

In witness whereof I have hereunto signed my name this fourteenth day of September 1908, in the presence of two subscribing wit' HQSSBS- FRIEDRlCH LUDWIG SCHMIDT.

Witnesses: v

HENRY HASPER, WoLnEMAR HAUPT. 

